As the environmental and economic costs of conventional power sources rise, there is an increasing interest in developing environmentally friendly and cost-effective energy sources. Devices such as solar cells and solar panels have been used to convert natural sunlight into electric energy. As another example, wind turbines may be used to harness natural air currents and convert kinetic energy to electric energy. However, there are drawbacks to these systems. For example, solar cells may be inefficient when sunlight is indirect, for example on cloudy days. Further, the efficiency of wind turbines generally may depend on location, as the turbines are most effective in an area that receives high or frequent winds.
Wind occurs naturally due, in large part, to the sun's energy. When the sun warms the earth's surface, air directly above the earth's surface warms as well. The warmed air expands with a lower density than surrounding air, and the warmed air therefore rises. As warmed air rises, pressure differences cause the surrounding air to fill the space left by the rising warm air. This process of rising air results in wind currents.